Apparatus for balancing rotating parts of machines



gain-wait cm amemzw Nov. 10, 1942. N. v. KOLESNIK APPARATUS FOR BALANCING ROTATING PARTS OF MACHINES Filed Feb. 27, 1940 Patented Nov. 10, 1942 APPARATUS FOR BALANCING ROTATING PARTS OF MACHINES Nikolai Vasilyevitch Kolesnik, Leningrad, Union of Soviet Socialist Republics Application February 27, 1940, Serial No. 321,088.

In the Union of Soviet Socialist Republics February 3, 1939 4 Claims.

An essential condition for good operation of a machine is that its moving parts be properly balanced.

Up to the present time, different types of apparatus have been proposed for eliminating misbalance of different parts of a machine. This misbalance however sometimes remains after the part has been made or sometimes appears after it has been in operation. The abovementioned balancing apparatus, however, only serve to balance separate units of a machine during its assembly and very often the balancing operation (with turbine rotors, for example) is performed at speeds much lower than the normal operating speed of the assembled machine.

As a result the assembled machine is still in an unbalanced condition.

It frequently occurs that a properly assembled and balanced machine becomes unbalanced after aperiod of operation because the rotating parts wear away unevenly. Usually this misbalance cannot be removed without having to dismount the whole machine and rebalance all the rotating parts separately on special balancing machines.

In particular, grinding and polishing machines are subjected to this defect after having been in operation. This occurs because the grinding or polishing wheel, initially properly balanced, wears out unevenly due to its inhomogenous structure and rapidly loses balance. This requires frequent rebalancing of the stones, particularly those used for finishing grinds, and hence causes considerable loss of time since the wheels have to be removed from the machines and rebalanced separately. As a result it often occurs that, to save time, the work is performed with an unbalanced stone. This leads to poor quality of operation, waste of abrasive material and rapid deterioration of the machine as a whole.

It has often been proposed to use a stroboscopic method to visually disclose the source of misbalance of rapidly rotating parts of a machine. Even in this case the stroboscopic method was applied to special balancing machines and thus did not remove the defects mentioned above.

The proposed invention, on the contrary, aims to enable the balancing of the rotating parts to be performed on the assembled machine itself while it is operating. This enables the cause of the vibrations to be immediately discovered and measures be taken to remove it.

The complete device which serves to make and break the circuit of an inertialess light-source, e. g., a gas-discharge tube, is simply placed or attached to the body of the machine without the use of any special appliances. The device is extremely simple in construction, fully portable and is easily tuned over a wide range of speeds.

The device according to the present invention which is placed on any vibrating part of the machine being tested, consists of two contacts, one of which is rigidly attached to the body of the device while the other can vibrate freely with respect to the other and is supplied with a device for varying its period of free oscillations. When this device is placed upon a vibrating part of some machine, e. g., a bearing or bed plate of a steam or hydraulic turbine, a grinding machine, lathe, milling, polishing machines, etc., and the vibrating contact is tuned to resonance with the frequency of the vibrations transmitted to it from the unbalanced rotating part of the machine, this contact will have an oscillation amplitude much greater to 200 times) than the magnitude of the vibrations of the body of the device and the rigid contact attached to it. Each oscillation cycle will give one contact between the fixed and moving contact strips, thus causing the gas discharge tube to flash.

The intermittent illumination thus produced will make the rotating parts of the machine being tested to appear stationary and at the same time the position of the source of misbalance will be quite definitely ascertained.

The drawing shows one form of the device. Fig 1 gives a general view of the instrument placed on a machine being tested and its connections to the gas-discharge tube, Fig. 2 shows a general view of the contacting device; Fig. 3 a view of the device with the front plate removed and Fig. 4, a cross section of the device along the line AA on Fig. 3.

The device comprises a casing I (Fig. 1) in which as was stated above are situated a nonresonating contact 4 and a resonating contact 5 adapted to have its frequency of vibration varied over a wide range.

The complete instrument is placed on the bed 2 of the machine being tested whose part 3 has to be balanced. Contacts 4 and 5 are connected in circuit with an inertialess gas discharge tube 6--a neon tube for example.

The number 1 indicates the source of misbalance (superfluous mass) and 8 indicates means, such as detachable weights, for balancing 1.

The contacting device I, as was stated above, comprises a box I (Figs. 2, 3, 4) having a contact plate 4 afiixed to a spindle rotating with friction in a bearing. The contact plate 4 has the form of a pointer and can be deflected to one or in the sliding member I2 which can move vertically in a guide I3. The slide [2 has a hole with a screw thread engaging a vertical screw l4 having a knob l5. By turning the latter, the member l2 can be lifted or lowered, thus decreasing or increasing the free length of the springy plate H and varying the free period of oscillation of the system.

The slide I2 is furnished with an indicator [6 moving along a scale I! graduated in frequency values and showing the frequency to which the vibratin plate I I with its contact is tuned. Besides this the circumference of the knob i5 is provided with still finer divisions. A fixed scale [8 is placed in front of the pointers 4 and 5.

If the device I be now placed on the vibrating part of the machine being tested, the rotating part being marked with a radial chalk mark, the whole device will vibrate as a rigid system, should the vibrating spring be not tuned to resonance with the frequency of the machines vibrations. The distance between the rigid and flexible contacts will remain constant. However, if we turn the knob I5 of the screw [4 and change the free length of the springy contact 5 to make it resonate with the oscillations of the device I together with the body of the machine under test, the amplitude of the contact 5 vibrations will be greatly augmented (150-200 times) and each oscillation will bring it into contact with the rigid strip 4.

Turning knob 9 we can move contact 4 to the left and give it a position where the oscillating contact can touch it. The screw l4 may be adjusted to bring the contact 5 in to exact resonance. In this manner, by adjusting the spring plate II for maximum amplitude of oscillations and the contact 4 until it just makes contact, the scale [8 will show the relative amplitude of the vibrations of the machine being tested.

In the example shown in Fig. 1, the vibrations of the contact 5 of the device I take place transversely (horizontally) and lag behind the vibrations of the machine by 90 so that the centre of the extra mass causing misbalance of the rotating part will be at the point 1.

The lag of the vibrations of contact 5 behind the vibrations of the machine by 90 when the parts are in resonance is explained by the physical law, according to which the phase of oscillations of a body which possesses a mass, lags .by 90 behind the phase of the disturbin force, As an example, the maximum speed phase of a pendulum lags by 90 behind the maximum magnitude of the force, which acts upon the pendulum on a tangent to the trajectory (the components of gravity).

The oscillations of a machine which is fixed to a stationary frame occur in a horizontal direction and when the apparatus will determine the position of the rotating part which will show the maximum amplitude of the weight 5 on the pointer ll, tuned to resonance, it is ascertained that the unbalance is situated on the vertical.

If a line a be drawn on the rotating part, it will appear to be stationary when illuminated in the intermittent light of the gas discharge tube 6 since it will always be in the same position when the gas-discharge takes place. If we make a mark h on a non-rotating part of the machine opposite the position of line a, and on stopping the machine bring lines a and b into alignment, then we can find the radius on which the centre 1 of the misbalanced mass is located. As will be seen from the diagram the centre is underneath the device I. Having found the radial position of the extra weight it can be compensated for by suitable means. A second test in which due consideration is given to the increase in phase difference above between the vibrations of the machine and the sprin y contact 5 due to the elasticity of the latter, the self inductance of the lamp circuit, etc., will enable the machine to be balanced very exactly-up to the magnitude of vibrations of the machine within 4-5 microns-which is much more exact than practical considerations demand.

Obviously, by performing this operation in several places along a rotating body, e. g., a length of shafting, it should be possible to eliminate vibrations due to several sources of misbalance.

I claim:

1. In an apparatus for stroboscopically balancing rotating elements in a machine, a device comprising a frame for said apparatus to be placed on the bed of said machine, a rigid contact, an axle journalled in said frame on which said rigid contact is mounted, a vibrating contact to cooperate with said rigid contact mounted in said frame, means for tuning said vibrating contact to resonance with the vibrations of said machine, means for manually rotating said axle to move said rigid contact to a position corresponding to the amplitude of the oscillations of said vibrating contact and means for indicating the value of the amplitude of the oscillations of said vibrating contact relative to said rigid contact when said vibrating contact is tuned to resonance.

2. In an apparatus for stroboscopically balancing rotating elements in a machine, a device comprising a frame for said apparatus to be placed on the bed of said machine, a rigid contact, an axle journalled in said frame on which said rigid contact is mounted, a vibrating contact to cooperate with said rigid contact mounted in said frame, means for tuning said vibrating contact to resonance with the vibrations of said machine, said axle being frictionally held in said frame, a knob on said axle for manually rotating said axle to move said rigid contact to a position corresponding to the amplitude of the oscillations of said vibrating contact and a scale showing the value of the amplitude of the oscillations of said vibrating contact relative to said rigid contact when said vibrating contact is tuned to resonance.

3. In an apparatus for stroboscopically balancing rotating elements in a machine, a device comprising a casing, an adjustable rigid contact mounted in said casing, a vibrating contact to cooperate with said rigid contact, means for moving said rigid contact to a position corresponding to the amplitude of the oscillations of said vibrating contact, a scale fixed in said casing graduated over the arc of a circle to indicate the position of said rigid contact, said vibrating contact comprising a resilient plate, a weight fixed to said plate at one end thereof, the other end of said plate being fixed to said casing, a slide frictionally movable along said plate for tuning said plate, a vertical scale in said casing and a pointer on said slide cooperating with said vertical scale.

4. In an apparatus for stroboscopically balancing rotating elements in a machine, a device comprising a, casing, an adjustable rigid contact mounted in said casing, a vibrating contact to cooperate with said rigid contact, means for moving said rigid contact to a position corresponding to the amplitude of the oscillations of said vibrating contact, a scale fixed in said casing graduated over the arc of a circle to indicate the position of said rigid contact, said vibrating contact comprising a resilient plate, a

weight fixed to said plate at one end thereof, the other end of said plate being fixed to said casing, a slide frictionally movable along said plate for tuning said plate, a vertical scale in said casing, a pointer on said slide cooperating with said vertical scale, said slide having a threaded aperture therein, a screw extending outside said casing cooperating with said threaded aperture for moving said slide along said plate and a knob fixed to said screw for manually operating said slide,

NIKOLAI VASILYEVITCH KOLESNIK. 

